Method of producing composite yarn



fabric having substantial stretchability.

METHOD -OF PRODUCING CORIPOSITE YARN William I. Leath, Charlotte, N. C.,and Frank E. Bobo, Jr., Gainesvilie, Ga, assignors, by mesneassignments, to 'Chadolon, Inc, Charlette, N. C., a corporation of NorthCarolina No Drawing. Original application August 3, 1954, Serial No.447,600. Divided and this application September 2, 1954, Serial No.453,761

'7 Claims. (01. 57-457 This invention relates to textile products andmethods and more particularly to the production of yarns havingdifferent twists and tendencies to untwist in opposite directions andthe knitting of these yarns separately and in opposing relationship toprovide a balanced knitted This fabric may be knitted so as to formladies full fashion or seamless hose, or may be knitted or woven toproduce ladies" underwear or other garments where stretchability of thegarment is desirable.

For illustrative purposes the invention will be described hereafter asapplied to the production of ladies hose, a presently importantcommercial embodiment, but without limiting the scope of the inventionthereto. Also forsake of brevity, the use of the yarn will be describedhereafter in connection with knitting operations, but it is to beunderstood that thisis byway of illustration and not limitation, andthat the yarn may be used in weaving or other textile operations.

One of the important features of the knitted fabric manufactured fromthis yarn is the balanced or rel'axed construction that avoids puckeringor uneven contraction along the length or width of the fabric, therebyenabling it to lie flat and undistorted so that the hose or othergarment made therefrom will assume its usual shape and desiredappearance and will differ only in size and stretchability from the samegarment knitted in conventional fashion.

An advantageous feature of the ladies hose made in accordance with thisinvention is the sheerness or dil'aphanous character of the hose thatresults from knitting of separate, unplied low denier yarn ends.

Prior attempts to produce ladies .lrose from yarn having substantialstretch characteristics have not provcn commercially successful becausethe hose were opaque, heavy and unattractive in appearance. The yarnused for producing these non-sheer hose was doubled, plied yarn having'two yarn ends highly twisted in opposite directions and plied together.This type of highly twisted and plied yarn contains a multiplicity ofsmall coils that give the yarn stretchability characteristics and whichcoils are pulled out or elongated when the yarn is stretched.

A characteristic feature of the yarn of the present invention is awildness or liveliness, i. e., a tendency to twist or form loops, whichis induced in the yarn by certain twisting and heat-setting operations.This liveli-ness or wildness in the yarn does not produce themultiplicity of small coils that characterize the abovementioned hightwist yarn and which coils require doubling or plying with a similarhigh twist yarn. However, the liveliness does require temporaryrestraining of the yarn to permit knitting or weaving of the yarn insingle ends to produce a sheer knitted fabric for ladies hosiery,panties, etc. This temporary control of ,the yarn, required for knittingor weaving operations, may be effected by temporarily plying with thetwisted lively yarn, a different type of untwisted yarn that will exerta restraining efiect on the wildness of the twisted yarn,

2,711 ,627 Patented June 28, 1955 ICC so that it can be managedsatisfactorily in the knitting machine or loom.

A presently preferred restraining type of yarn for temporarily holdingthe twisted yarn, is silk, particularly because of its adaptability forknitting with the same machines and equipment used for knitting thetwisted, main yarn. Also the silk is further adapted for removal afterthe knitting operation by dissolving with a suitable chemical such as,for example, caustic soda. Another type of temporary restraining yarnthat might be used for plying with the twisted yarn and which can besubsequently removed by dissolving with suitable chemicals, e. g.,acetone or acetic acid, is cellulose acetate. Likewise, any othernatural or synthetic fiber yarn that would serve the above purpose andcould be removed thereafter is also contemplated for use in the methodof this invention.

Regarding the main or permanent yarn to be used for forming thestretchable knitted fabric of this invention, including ladies hosiery,underwear, etc., the present commercially advantageous type of yarn isnylon, commonly used today for knitting such garments. Although nylonyarn is the logical choice at present because of its technicalcharacteristics and commercial availability, other synthetic yarns, forexample those known in the trade as DACRON (a condensation polymer ofterephthalic acid and ethylene glycol) and dynel (a polymer of vinylchloride and acrylonitrile), might be used, as well as other suitablesynthetic or natural fiber yarns. The following description refersparticularly to nylon yarn but by way of illustration only.

The above-mentioned prior art types of ladies" stretchable hose areproduced from multifilament nylon yarns, and this is consideredessential in view of the high twist to which those yarns are subjected,i. e., approximately turns. This high order of twist in one direction,followed by an equal or greater number of twists in the oppositedirection, produces the above-mentioned multiplicity of small coils inthe multifilament yarn. This coiled structure, as well as the extremewildness of the yarn so produced, requires plying of two ends of thisyarn having opposite twists, so that the series of coils in one yarn endmeshes or entwines with the series of coils in the other yarn end ofopposite twist. By this arrangement one twist neutralizes or offsets theother twist and thereby produces a relaxed, double, plied yarn havingstretchability but nevertheless being subject to the disadvantages ofcausing puckering, deformation, and non-Sheerness in the knitted fabric.

The yarn and twisting methods of the present invention are not limitedto multifilament yarns, but employ equally as well the monofilamenttypes of yarns. Thus, ladies sheer nylon hose of the most popular typetoday can be knitted from 15 denier monofilament nylon yarn that hasbeen subjected to the desired twisting and setting operations and pliedwith a silk or other temporary restraining yarn. These operationscomprise, generally, a first twisting of one end of the nylon yarn,multifilament or monofilament, in one direction, say to the right, so asto provide an S twist, then heating to a temperature sufficient to setthe yarn and which temperature will be higher than all subsequentlyencountered temperatures in the treatment of the yarn or product madetherefrom, followed by twisting the yarn in the opposite direction, thatis to the left, and providing therein a Z twist. This reverse orbacktwisting operation will determine principally the amount ofliveliness or wildness in the yarn and the extent of twist will dependupon the degree of this property desired in the yarn.

The first twist applied to the yarn as described just above may varysubstantially in extent, or number of twists applied, a typical rangebeing 20 to 50 turns twist. At the end of this first twisting operation,especially if as many as 40 or 50 or more turns are applied, the twistedyarn will possess a substantial liveliness or wildness sufiicient toform a stretchable fabric, upon plying with a temporary restraining yarnand knitting or weaving. However, subsequent high temperature treatmentsof the twisted yarn or fabric produced therefrom, such as normally occurin the manufacture of full fashioned hosiery, would substantially removethe lively characteristics and stretchability of the yarn or fabricbecause of the fact that the yarn at this stage, immediately after thefirst twisting, has not been set with heat. Thus it is important incarrying out the method of this invention, to incorporate a heat-settingof the nylon yarn at an appropriate point and to have this heat-settingoperation carried out at a temperature appreciably higher than anysubsequently encountered temperature.

As above indicated, it is important, and in fact essential, to heat-setthe yarn at the proper time and at an adequate temperature to avoidlosing the lively effects induced in the yarn by the twisting operationwhen the hose knitted therefrom are subjected to subsequent highertemperature treatments. In the method of this invention, thisheat-setting treatment may be carried out after the first twistingoperation and prior to the second or backtwisting operation and, infact, this is the presently preferred procedure. However, worth-whilebenefits may be obtained from the method of this invention when carriedout as described above except for changing the time or point in theprocess of the heat-setting operation. For example, we have producedyarn having substantial stretchability and produced ladies fullfashioned hose therefrom, in which the heat treating operation wasapplied to the yarn prior to twisting of the yarn. In this modification,no second or reverse twisting of the yarn is required; only the initialheat treating, followed by twisting the desired number of turns such as,for example, about 50 turns.

In the manufacture of nylon full fashioned hosiery, the twisted yarnwould usually be heat-set at a temperature of about 270 F. for asufiicient length of time, c. g., one half hour, to effect the desiredheat-setting. This heatsetting temperature could be higher if desired,but the important point is the use of a temperature sufficiently higherthan the subsequent processing temperatures to avoid damaging effects ofthe latter. In the manufacture of full fashioned hosiery, the subsequentprocessing temperatures encountered in the dyeing and finishingoperations are in the order of 250 F. or about 20 lower than theabove-mentioned 270 F. heatsetting temperature, which is found to be asafe margin. If the subsequent temperature equals or exceeds theprevious heat-setting temperature, the twist effect in the yarn will besubstantially completely lost.

Another important feature of the twisting and heatsetting operations ofthis invention is that of twisting the yarn adequately following thefirst twisting and heatsetting operations, because the heat-settingoperation substantially removes or neutralizes the liveliness impartedto the yarn by the first twisting operation. This being so, the yarn,after heat-setting, requires further twisting to etfect the desiredliveliness. The amount of twisting employed after heat-settin willdepend upon the desired degree of liveliness or stretchability desiredin the yarn or fabric made therefrom. This twisting after heat-settingmay vary substantially as to the number of twists and may be of theorder of the first twisting operation described above prior toheat-setting. In other words, a typical number of twists for this secondtwisting operation would be 30 to 50 turns or higher. Usually it isdesirable to employ a somewhat higher number of twists in the secondtwisting operation than in the original twisting operation. For example,if the yarn is originally twisted about 40 to 50 turns, the secondtwisting operation, after heatsetting, might be in the order of 50 toturns.

Also, it is usually of advantage to employ in this second twistingoperation, a twist that is opposite in direction to the original twist,i. e., a Z twist for the second twistmg operation where an S twist hasbeen employed in the original twisting operation. A reverse or backtwist of this type, after heat-setting, will increase desirably theliveliness in the yarn as compared to a continuation of twist in thesame direction as the original twist. Furthermore, the strength andother physical properties of the yarn will be better maintained by useof a reverse or back twist for the second twisting operation.

When multifilament yarns are used in these twisting operations, it isimportant to extend the reverse or back twisting operation at least somefew turns more than the twist in the original twisting operation, sothat the several filaments comprising the yarn will be integrated morecompletely by the additional turns twist than would be the case if theback twist equaled the forward twist and left the filaments insubstantially untwisted or parallel position. This filament difficultydoes not arise, of course, when monofilament yarns are used, but evenwith such yarns it has been found desirable to utilize a somewhat moreextensive reverse twist than the original twist and thereby obtain agreater liveliness in the yarn. Following the above-described threesteps of first twistmg about 40 to 50 turns in one direction, thenheat-setting and twisting about 50 to 60 turns in the reverse direction,the yarn will possess such liveliness that it could not be handledpractically in the knitting or weaving operation. At this point, it isthen necessary to ply the yarn temporarily with silk or otherrestraining yarn, as above mentioned.

In carrying out this plying operation, the twisted nylon yarn is pliedwith the restraining yarn by twisting the two yarns together for arelatively few turns, such as, for example, 5 to 20 turns. A highernumber of turns twist for this plying operation could be employed if itis desired, although it is not usually necessary. The plying twist 1susually in the direction of the original twist and therefore opposite tothe direction of the twist after heatsetting. More specific butnon-limiting examples of the twistmg and heat-setting operationsdescribed generally above, WhICh we have employed satisfactorily in theproduction of yarn for knitting ladies sheer nylon stretchable hose, areas follows:

One end of monofilament nylon yarn is twisted 30 turns per inch in a Zor left twist direction. Another end of the same nylon yarn is twisted30 turns per inch in an S or right twist direction. These two separatelytwisted nylon yarns are subjected to treatment with live steam insuitable equipment such as a pressure or vacuum retort and at atemperature of approximately 265 F.270 F. for a sufficient length oftime to effect proper penetration. After this treatment with live steam,the yarn is transferred to twister bobbins and twisted 37 turns in theopposite direction of the original twist. As a consequence of thistwisting operation, the yarn is very lively or wild and could not besatisfactorily knitted in this condition, and it is therefore plied withthe silk yarn as above mentioned, the details of which are as follows:

The yarn that was twisted originally 30 turns to the left, Z twist, thenbacktwisted 37 turns to the right, S twist, is plied with one end ofsilk of either 13/ 15 or 20/22 size, and the plied yarns given a totalof approximately 14 turns to the left, Z twist. The other yarn, whichwas originally first twisted 30 turns to the right, 8 twist, thenbacktwisted 37 turns to the left, Z twist, is now plied with one end ofthe silk yarn and the plied construction given a total of 14 turns twistto the right, S twist. This plying of the nylon and silk yarns may becarried out in one or more stages on conventional twisting machines.This silk will usually be treated prior tion.

to plying with conventional silk soaking treatment, followed by dryingand skein winding. Also, it is not necessary to impart any twist to thesilk yarn.

To prepare the nylon yarn which is to be plied with the silk yarn, itwill be understood from the foregoing that bobbins, spools, p'irns orother suitable carriers of the nylon yarn will be used and one or moreof these carriers will contain the nylon yarn twisted in one directionand another carrier will contain a supply of the yarn twisted in theopposite direction.

The plying of the twisted lively nylon yarn with silk or other suitableyarn restrains the liveliness as described above and thereby enables theyarn to be handled satisfactorily in knitting ladies hose. However, oncethe silk or other restraining yarn is removed from the knittedstructure, the yarn will again become lively and this requires knittingof the yarn in a manner suitable to restrain somewhat this livelycharacteristic in the knitted structure. For that purpose, yarns ofopposite twist, prepared as described above, are used in counteractingrelationship while at the same time avoiding plying of the yarns and theadverse effects thereof. Instead of plying these yarns of opposite twistas has been done heretofore, they are knitted singly in alternatingcourses or groups of courses, as above mentioned. In other words, theyarn which has a final S twist is used for knitting one or severalcourses and the yarn that has the opposite or Z twist is used forknitting the next adjacent course or several courses. In this manner,the courses of yarn that tend to untwist to the left are counterbalancedto some extent by the adjacent courses of yarn that tend to untwist tothe right, and this results in the balanced knitted fabric or structurementioned above when these alternating courses recur throughout thelength of the fabric, such as the length of a knitted full fashionedladies hose.

The knitting operation may be carried out on conventional knittingmachines of the full fashioned hosiery type, and the separate left andright twisted yarns (plied with silk) are knitted in an alternatingpattern; for example, two courses of the nylon and silk plied yarncontaining an S twist are first knitted, followed by two courses ofnylon and silk plied yarn containing the Z twist. 7

We have found in commercial practice that knitting of these oppositelytwisted yarns may advantageously be carried out in alternating pairs ofcourses, that is, two courses knitted with left twist yarns and the nexttwo courses knitted with right twist yarns and this alternation repeatedthroughout the length of the fabric. This paired arrangement is bestsuited for the usual types of full fashioned knitting machines, but itis to be understood that the courses may be alternated singly instead ofin pairs. On the other hand, a greater number of courses, such as 4 or 6courses, of yarn of one twist may be alternated with a similar number ofcourses of yarn of the opposite twist.

Although this alternation of courses of opposite twist yarnssufficiently counteracts the torsional forces of these two yarns toprevent puckering or distortion of the fabric generally, the fabricformed in this manner has sufiicient distortion or liveliness in theindividual stitches or loops to impart substantial stretchability. As anillustrative example of this stretchability, a ladies hose composed ofthe fabric of this invention can be stretched as much as 50% to 100% ormore of its original length without permanent deformation of thestitches or loops, and has the property of contracting to substantiallyits original length when the stretching tension is removed.

The present-day sheer type of ladies hose normally uses nylon yarn ofnot greater than 30 denier and the yarn most commonly used is 15 deniernylon yarn, although 12 denier and denier nylon yarns are available andthese yarns or even lower denier yarns may be employed in producingladies sheer hosiery in accordance with this inven- Ladies hose madewith nylon yarn as high as degree of sheerness.

30 denier, in accordance with this invention, possess a Similarly, .hoseknitted with substantially higher denier yarns, such as 70 denier orhigher, and which are known in the trade as service weight" hose, maylikewise be knitted fom the stretchable yarn of this invention.

One of the attractive features of ladies hose produced from this yarn,irrespective of the denier used, is that the hose have substantially thesame appearance as hose knitted from conventional yarn of the variousdeniers, which is in distinct contrast to hose knitted from theabovementioned highly twisted and plied yarns, such as yarn composed oftwo plies of 20 denier each.

Following the knitting, seaming with a yarn constructed so as to give acomparable stretch to that of the stocking yarn, and other usual greygoods operations before dyeing of the knitted hose, they are subjectedto a treatment with caustic soda which removes the silk from the hose,leaving the nylon unharmed. Although subject to variations, details of atypical caustic stripping operation of this type are as follows:

The stockings in the greige are placed in nets such as are normally usedin processing and subjected to treatment in 0.75% to 1.0% solution ofsodium hydroxide in water for approximately one hour at 210 F., or untilthe silk is dissolved. The dissolved silk is removed by washing withwater, following which the hose are dyed and the excess moistureremoved. The hose are then pulled over a boarding form of restrictedsize to straighten but not to stretch the hose. Subsequent finishingoperations, including inspection and packaging of the hose for sale, arecarried out in the regular manner.

This application is a division of our copending application Serial No.447,600, filed August 3, 1954, and claims only the method of producingthe composite yarn, the composite yarn product being claimed in ourapplication Serial No. 453,783, filed concurrently herewith, .and thetextile products utilizing the composite yarn being claimed in ourapplication Serial No. 447,600, filed August 3, 1954.

Throughout the specification and claims herein in each instance wherereference is made to turns in the twisted yarn, it is to be understoodthat this is based upon turns per inch, as already stated in oneinstance herein above.

Various modifications and changes may be made in the above-describedmaterials, products and methods without departing from the scope of thisinvention as defined in the appended claims.

We claim:

1. A method of producing lively yarn adapted for the productiontherefrom of knitted and woven textile products, comprising firsttwisting nylon yarn about 20 to 50 turns per inch sufficient to induce asubstantial liveliness in the yarn, subjecting the twisted yarn to anelevated temperature to heat-set the yarn and stabilize it againstsubsequently encountered elevated temperatures, then twisting theheat-set yarn in a direction opposite to that of the first twist, about30 to 60 turns per inch without further heat setting, and then plyingthe twisted yarn with a temporary restraining yarn in a directionopposite to the direction of the said last twist that subdues theliveliness of the twisted yarn and enables practical handling thereof inknitting and weaving operations.

2. The method of claim 1 in which said nylon yarn is a monofilamentyarn.

3. The method of claim 1 in which said elevated temperature isapproximately 270 F.

4. The method of claim 3 in which said twisted yarn is subjected to saidelevated temperature for approximately /2 hour.

5. The method of claim 1 in which said yarn is twisted a higher numberof turns per inch by the second twist than by the first twist.

6. The method of claim 1 in which said yarn is twisted 7 40 to 50 turnsper inch by the first twist and 50 to 60 turns per inch by the secondtwist.

7. The method of claim 1 in which said plying of said twisted yarn withsaid temporary restraining yarn consists of 5 to 20 turns per inch. 5

References Cited in the file of this patent UNITED STATES PATENTS2,295,593 Miles Sept. 15, 1942 10 8 Meade Oct. 26, 1943 Hathorne et a1.July 18, 1944 Dorgin Nov. 13, 1951 Neumager June 16, 1953 Brooks June 1,1954 FOREIGN PATENTS Great Britain Ian, 2, 1945 Great Britain Feb. 2,1948

1. A METHOD OF PRODUCING LIVELY YARN ADAPTED FOR THE PRODUCTIONTHEREFROM OF KNITTED AND WOVEN TEXTILE PRODUCTS, COMPRISING FIRSTTWISTING NYLON YARN ABOUT 20 TO 50 TURNS PER INCH SUFFICIENT TO INDUCE ASUBSTANTIAL LIVELINESS IN THE YARN, SUBJECTING THE TWISTED YARN TO ANELEVATED TEMPERATURE TO HEAT-SET THE YARN AND STABILIZED IT AGAINSTSUBSEQUENTLY ENCOUNTERED ELEVATED TEMPERATURES, THEN TWISTING THEHEAT-SET YARN IN A DIRECTION OPPOSITE TO THAT OF THE FIRST TWIST, ABOUT30 TO 60 TURNS PER INCH WITHOUT FURTHER HEAT SETTING, AND THEN PLYINGTHE TWISTED YARN WITH A TEMPORARY RESTRAINING YARN IN A DIRECTIONOPPOSITE TO THE DIRECTION OF THE SAID LAST TWIST THAT PRACTICAL THELIVELINESS OF THE TWISTED YARN AND ENABLES PRACTICAL HANDLING THEREOF INKNITTING AND WEAVING OPERATIONS.